Heretofore, record materials, i.e., pressure sensitive copy materials have been known which are each composed of a paper coated on one side thereof with microcapsules containing a colorless electron donating agent (hereinafter referred to as "color former") in a solution and another paper coated on the other side thereof with an electron accepting substance (hereinafter referred to as "developer") such as an acidic inorganic material or a carboxylic acid having an ability to develop a color by the reaction with the aforesaid color former When used, both the papers are superposed on each other so that the respective coated surfaces thereof may face each other, and pressure is then applied onto the superposed papers, so that a copy record is given thereby.
This type of record material has the following copy record mechanism: The microcapsules on the paper are ruptured by the pressure from a pen, a typewriter or the like in order to release a color former solution therefrom, and the latter is then brought into contact with the developer with which the confronted paper has been coated, whereby a color is developed.
Furthermore, another type of record material has also been known in which the respective coating materials of the microcapsules and the developer having such a color developing mechanism are applied onto either surface of one paper.
The color former solution used in the aforesaid record material is a solution in which the electron donating color former is dissolved in one or more hydrophobic solvents. The hydrophobic solvent used herein should satisfy the following requirements:
(1) To be nontoxic,
(2) to have no uncomfortable odor,
(3) to be colorless or to have a very faint color,
(4) to dissolve the coupler sufficiently and to be excellent in stability,
(5) to permit forming microcapsules with ease,
(6) to ensure the storage stability of the microcapsules,
(7) to allow a color developing reaction to occur and to accelerate color development velocity,
(8) to permit providing color-developed images without blotting, and to ensure the formation of the clear color-developed images, even after stored for a long period of time, and
(9) to be inexpensive.
Examples of the solvent for this kind of record material which have been heretofore used include diarylalkanes such as phenylxylylethane and phenylethylphenylethane, aromatic hydrocarbon oils having plural aromatic rings such as an alkylnaphthalene, an alkylbiphenyl and a partially hydrogenated terphenyl, and chlorinated paraffins.
However, these solvents are expensive, and the pressure sensitive copy materials obtained by using such solvents do not always satisfy the requirement of color development velocity.
The present invention provides a pressure sensitive copy material which can solve the above-mentioned problems of the conventional pressure sensitive copy materials and which is excellent in color development performance and inexpensive.
The pressure sensitive copy material of the present invention can be prepared by combining a specific solvent satisfying the above-mentioned requirements with a specific developer. Particularly, in the inexpensive pressure sensitive copy material of the present invention, an improvement is made in the color development velocity at a low temperature which is one drawback of the conventional pressure sensitive copy materials. It should be noted that in this specification, boiling points mean values in terms of atmospheric pressure, unless otherwise noted.